erofs: refine managed inode stuffs

Set up the correct gfp mask and use it instead of hard coding.
Also add comments about .invalidatepage() to show more details.

Link: https://lore.kernel.org/r/20220310182743.102365-2-hsiangkao@linux.alibaba.comReviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

fs/erofs/super.c

@@ -532,6 +532,11 @@ static int erofs_managed_cache_releasepage(struct page *page, gfp_t gfp_mask)
 	return ret;
 }
 
+/*
+ * It will be called only on inode eviction. In case that there are still some
+ * decompression requests in progress, wait with rescheduling for a bit here.
+ * We could introduce an extra locking instead but it seems unnecessary.
+ */
 static void erofs_managed_cache_invalidatepage(struct page *page,
 					       unsigned int offset,
 					       unsigned int length)
@@ -565,8 +570,7 @@ static int erofs_init_managed_cache(struct super_block *sb)
 	inode->i_size = OFFSET_MAX;
 
 	inode->i_mapping->a_ops = &managed_cache_aops;
-	mapping_set_gfp_mask(inode->i_mapping,
-			     GFP_NOFS | __GFP_HIGHMEM | __GFP_MOVABLE);
+	mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
 	sbi->managed_cache = inode;
 	return 0;
 }

fs/erofs/zdata.c

@@ -1091,10 +1091,10 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
 					       unsigned int nr,
 					       struct page **pagepool,
-					       struct address_space *mc,
-					       gfp_t gfp)
+					       struct address_space *mc)
 {
 	const pgoff_t index = pcl->obj.index;
+	gfp_t gfp = mapping_gfp_mask(mc);
 	bool tocache = false;
 
 	struct address_space *mapping;
@@ -1350,8 +1350,7 @@ static void z_erofs_submit_queue(struct super_block *sb,
 			struct page *page;
 
 			page = pickup_page_for_submission(pcl, i++, pagepool,
-							  MNGD_MAPPING(sbi),
-							  GFP_NOFS);
+							  MNGD_MAPPING(sbi));
 			if (!page)
 				continue;